1. Field of the Invention
The invention relates to electrical circuits for electric heating systems and, in particular, to systems in which a plurality of heating elements are sequentially energized by cascaded delay relays to avoid power line surges and in which a blower is maintained in operation by the circuit at all times during the sequential operation of the heating elements.
2. Description of the Prior Art
The prior art, as exemplified by U.S. Pat. Nos. 3,046,380; 3,242,978; 3,351,739; 3,588,471; 3,659,155 and 3,770,977 contains many circuits for sequential operation of electric heater elements wherein blower operation is maintained at all times when one or more electric heating elements are energized. In prior art circuits using three of more cascade energized delay relays for sequentially energizing a plurality of heating elements wherein a first of the relays controls blower motor operation, it has been necessary to utilize separate facilities, such as a heat sensor or an element current sensor, to maintain the first relay operated after the opening of a thermostatic switch to continue blower operation whenever any heating element is energized.